Thermographic copying material



Jan. 10, 1961 F. D. ALLEN ETAL 2,967,785

THERMOGRAPHIC COPYING MATERIAL Filed Aug. 14, 1959 lNDOLE COMPOUNDPHENOL COMPOUND SUPPO/P 7' INDOLE COMPOUND PHENOL COMPOUND /0 SUPPORT /04 SUPPORT /7\' PR/NTED CHARA arm /64 I ORIGINAL FRANK D. ALLEN JAMES A.VAN ALLAN JOHN J 8/1 GURA ZNVENTORS ATTORNEYS United States Patent '0THERMOGRAPHIC COPYING MATERIAL Frank D. Allen, James A. Van Allan, andJohn J. Sagura,

Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., acorporation of New Jersey Filed Aug. 14, 1959, Ser. No. 833,764

11 Claims. (Cl. 117-36) This invention relates to thermographic copyingmaterial and to a method of using the same.

Thermographic copying materials and methods have been previouslydescribed in a number of domestic and foreign patents. These materialsfrequently have the advantage of simplicity over certain photographicprocesses in that they produce a direct positive image of the originalupon exposing the heat-sensitive or thermographic copying material inheat conductive association with a graphic original to radiant energy(e.g., infrared radiation). However, certain of these thermographicmaterials which have been previously used are only slightly sensitive toheat, and, consequently, excessively intense exposures are necessary inorder to produce a facsimile copy. Other materials may not suffer fromthe aforementioned defect, but they are diflicult to use, or handle, inthat they contain metallic ions which might stain the material uponwhich the heat-sensitive layer is coated. Other thermographic orheat-sensitive materials have the disadvantage of being excessivelysensitive to ordinary light. Other heat-sensitive, copying materialsexhibit thermotrophy and lose their developed color when theheat-sensitive material is cooled to room temperature. It is immediatelyobvious that these heat-sensitive materials have only limited use, and,in certain instances, cannot be used at all if one desires to producefacsimile copies on a commercial scale.

While many of the thermographic methods of reproduction described in theprior art require that the plurality of heat-sensitive ingredients bemaintained in physically-distinct relationship, it is not alwaysnecessary, according to our invention, to separate physically theheatsensitive components in our compositions from one another.

The instant invention provides a convenient means of reproducing graphicoriginals by exposure of such originals in contact with certainheat-sensitive layers. The heat-sensitive layers useful in practicingour invention contain as an essential ingredient at least one indolederivative selected from those represented by the following generalformula:

wherein R represents a hydrogen atom or an alkyl group, such as methyl,ethyl, etc., Q and Q each represents the non-metallic atoms necessary tocomplete a monocyclic nucleus containing only one nitrogen atom, saidnucleus containing an unsubstituted carbon atom in the 3-position withrespect to said nitrogen atom, and D represents the atoms necessary tocomplete a benzene ring, which KIT may be substituted by alkyl (e.g.,methyl, ethyl, etc.), alkoxyl (methoxyl, ethoxyl, etc.), etc. Especiallyuseful compounds embraced by Formula I above include those representedby the following general formula:

wherein Q and Q each have the values given above. indole compoundsembraced by Formula II above include those represented by the followinggeneral formula:

wherein R R R and R each represents a hydrogen atom or a lower alkylgroup, e.g., methyl, ethyl, etc., and Z and Z each represents thenon-metallic atoms necessary to complete a monocyclic ring containingfrom 5 to 6 atoms in the ring, only one of said atoms in the monocyclicring being a nitrogen atom. Typical monocyclic nuclei defined by Q, Q Zand Z include pyrrolidine, piperidine, morpholine, etc., as well assubstituted derivatives thereof, including alkyl (e.g., methyl. ethyl,propyl, isopropyl, etc.), aryl (e.g., phenyl, tolyl, etc.), etc.,derivatives. Our invention is briefly illustrated in the accompanyingdrawing, wherein Figure 1 is a graphic reproduction of a heat-sensitivecopying material which can be processed according to our invention,while Figure 2 is a graphic reproduction of a second type ofheat-sensitive material which can be processed according to ourinvention, and

Figure 3 is a graphic reproduction of one method of exposing theheat-sensitive copying material illustrated in Figure 2, the copyingmaterial being in heat-conductive association with an original.

Exposure of a copying sheet comprising at least one of the indolecompounds represented by Formulas I, II, or Hz: in heat-conductiveassociation with a graphic original as hereinafter described results ina substantially immediate, visible color change. Infrared radiant energyhas been found to be particularly useful in practicing our invention,since such energy is readily obtainable from many illuminating sources.

It has been found that especially useful results can be obtained usingat least one of the above-formulated indole compounds, it these indolecompounds ,are associated wtih a compound containing a phenolic hydroxylgroup, or an organic compound which contains an enolize ableketomethylene group, including 5pyrazolone compounds containing ahydrogen atom in the 4-position, as well as compounds containing anextracyclic (acyclic) group. Use of one of these compounds containing a(III) wherein R represents an. alkyl, group or an aryl group (either ofwhich may be further substituted by additional organic substituents), Rrepresents a hydrogen atom or an alkyl group such as methyl, ethyl,etc., and X represents a hydrogen atom, a halogen atom (e.g., chlorine,bromine, etc.), or a non-basic organic substituent (e.g., methyl, ethyl,etc.). The term non-basic is intended to define substituentsother thanan amino nitrogen-containing group.

The heat-sensitive material forming the heat-sensitive areas of thecopying sheets of our invention can be coated on any suitable support,especially supports having low thermal conductivity, such as paper. Ingeneral, we prefer to use ordinary paper as a support for theheat-sensitive materials, and the paper can be transparent, translucent,or opaque. Of course, it is frequently desirable to use a support whichtransmits the exposing radiation, especially where the graphic originaldoes not transmit such radiation (i.e., at least one of these shouldtransmit radiation).

As indicated above, the. indole compounds of Formulas I, II or Ila canbe used alone as the heat-sensitive materials, or they can be used incombination with the phenolic compounds, pyrazolone compounds, orcompounds containing an acylic ketomethylene group. When theheat-sensitive indole compounds are used in combination with thephenolic compounds, pyrazolone compounds or compounds containing anacyclic ketomethylene. group, the ratio of the components in theheatsensitive system can vary, depending upon the particular materials,effects desired, etc. In some instances, it is desirableto incorporatethe indole compounds in a layer distinct from the layer containing thephenolic compound, pyrazolone compound, or compound containing theacyclic ketomethylene group, since spontaneous color formation may occurif the two components are intimately associated in the same layer. Inother instances, particularly with the compounds of Formula III, bothcomponents can be dispersed in a common solvent and coated onto thesupport from the same solution without any spontaneous color formationtaking place.

It is thus apparent that the heat-sensitive layers useful in ourinvention can be prepared in several ways depending upon the use towhich the heat-sensitive copying sheet is to be put. In its simplestform, the invention contemplates the application of a solution of atleastone of the above-formulated indole compounds to the support,followed by evaporation of the solvent from the coating solution. Inanother variation of the invention, a second solution containing thesecond component (the phenolic compound, pyrazolone compound, orcompound containing an extracyclic ketomethylene group) of theheatsensitive material can be applied to the copying sheet and thesolvent evaporated from this second coating solution. Of course, thismethod of operation cannot be employed if the second component undergoessubstantially,

immediate reaction with the indole compound to produce a color product.Useful results have been obtained where the second solvent is selectedso that only one of thecomponents isv soluble in that solvent, or thefirst componenthastoo low a solubility to cause a harmfuleffect.

If desired, the components of the heat-sensitive system can beincorporated in an inert vehicle by simply adding these components. to asolution of the inert vehicle. Useful inert vehicles include esters ofcellulose, cellulose ethers (e.g., ethyl cellulose, etc.), polyvinylresins (e.g., polyvinyl chloride, polystyrene, polymethylmethacrylate,polyvinyl acetate, as well as copolymers of these polymeric materials),etc. In some instances, it may be desirable for the reasons indicatedabove, to incorporate the components of the heat-sensitive system inseparate contiguous layers. It is immaterial which layer is applied tothe support first. The heat-sensitive copying sheets of our inventioncan be, treated with solutions designed to provide a protective overcoatfor the heatsensitive layers. For instance, after application of theheat-sensitive material to. the. copying sheet, a solution of gelatin orother organic material can be applied over the heat-sensitive material.The layers of the heat-sensitive materials can contain inert pigmentsfor the purpose of increasing the contrast of the final copy. Forinstance, an opaque layer may be applied over the heat-sensitivecomponents, or an opaque layer may be applied on the reverse side of thecopying sheet.

Typical compounds which can be employed together with the indolecompounds of our invention in order to lower the reaction. temperatureinclude the following:

(1) Z-acetamidophenol (2) 2-acetan1ido-4-chlorophenol (3.)2-acetamido-4,6-dichlorophenol (4)2-acetamido-4,6-dichloro-5-methylpheno1 (5)2-benzamido-4,6-dichloro-5-methylphenol (6) 2 (2,4 ditert.amylphenoxyacetamino) 4,6-

dichloro-S-methylphenol (7) 6 [a {4 [a (2,4 di tert. amylphenoxy)-butyramido]phenoxy} acetamido] 2,4 dichloro S-methylphenol (8)2-[a-(3-pentadecylphenoxy)butyramidolphenol (9) a (4 tert. amylphenoxy)2 hydroxy 5 phenylazobutyranilide (10) 2 [a 2,4 di tert.amylphenoxybutyrylaminol- 4,6-dichloro-S-methylphenol (11) 4 chloro 1hydroxy 2 [a (2,4 di tert.-

amylphenoxy)-n-butyllnaphthamide (12) 4 (p tert. butylphenoxy) 1 hydroxy4- phenylazo-2-naphthanilide (l3) 1 p (p tert butylphenoxyphenyl) 3 [3ptert.-amylphenoxy)-benzoylamino]-5-pyrazolone (l4) 1 (2,4,6trichlorophenyl) 3 pentadecyl 4- chloro-S-pyrazolone (15) 1 (2,4,6trichlorophenyl) 3 pentadecyl 4- bromo-S-pyrazolone ('16) 1 (2;4,6trichlorophenyl) 3 [3' (2",4" ditert. amyl phenoxyacetamido)benzamido] 4(pmethoxyphenylazo)-5-pyrazolone (l7) 1 (p tert. butylphenoxy)phenyl 3 a(ptert. butylphenoxy) propionylamino 4 (p methoxyphenylazo) 5'pyrazolone(18) N (4 benzoylacetaminobenzenesulfonyl) N-('y-phenylpropyl)-p-toluidine (19) a (o Methoxybenzoyl) 4 [a (2,4 ditert.-

amylphenoxy)-butyra.mido]acetanilide (20) Gentisic acid (21)Gentisanilide (22) Tetrachlorohydroquinone (23) 2,5-dichlorohydroquinone(24) Monochlorohydroquinone 25) 2,2-bis (4-hydroxy-3 ,5 -dichlorophenyl)propane (26) 2,2-bis(4-hydroxy-3;5-dibromophenyl) propane (27) Eethylgentisate (28) Methyl gentisate (29) p-Hydroxybenzaldehyde (30)Vanillin.

(31 Resorcinol (32) Halogenated phenols (mixture) Typical indolecompounds which can be employed in our. inventioninclude those listed inthe following table.

These indole compounds were prepared'bydissolving isatin or an isatinderivative. ina suitableorganic solvent,

such as methanol, and bringing the solution "to a boil. The appropriatesecondary heterocyclic amine was added to the solution and the solutionwarmed on a steam cone until the desired product crystallized. Thesolution was then cooled to room temperature and the desired productseparated by filtration, washed with solvent, such as methanol, anddried. The following table identifies indole compounds of Formula I andgive the melting point and chemical analysis thereof.

isatin-3-dipiperidide and the coating dried. The coated side ofthe'paper was then exposed through a typewritten sheet to infraredradiation in a thermographic duplicating device of the type described inMiller U.S. Patent 2,740,895, issued December 22, 1953. A copy of theoriginal was obtained as a blue image in a matter of seconds.

Example 3 (Formula I) RmgA I Dichlorohydr-oquinone was dissolved in asolution of Vinylite VYLF resin as described in Example 2 and thencoated on an ordinary paper support. The dry 9 layer was then overcoatedwith a methanol solutionof BingB polyvinyl butyral resin containingisatin-3-dipiperidide. N/ The coating was then dried and placed incontact with a graphic original and passed through a thermographic Rcopying device as described in Example 2. A copy of the TABLE AnalysisIndole M.P.,

No. R Ring A Ring B C. Calcd. Found 0 H N o H N piperidlne piperldine222-4 72.3 8.4 14.1 72.2 8.4 14.2 3-tnethylpiperidlne-3-methylplperldlne.. 150 73.5 8.9 12.9 73.2 8.8 12.64-rnethylpiperidine. 4-methylpiperidina- 154.6 73.5 8.9 12.9 73.1 9.012.8 4-ethylpiperidine 4-ethylpiperidiue 145 74.4 9.3 11.8 75.2 9.24-phenylpiperidine 4-phenylpiperidine-.. 104.7 morpholine morpholine184-5 63.4 7 0 13.8 63.6 7.3 14.1 pyrrolidine pyrrolidine 134-6 70.9 7.815.5 70.8 8.0 15.6 mor piper 205-8 67.8 7.7 13.9 68.2 7.7 13.7 pyrmliinn dd 152-5 71.6 8.1 14.7 71.8 8.0 14.9 d0 morphollne 13840 67.0 7.414.6 67.4 7.2 14.9 mor do 195 64.4 7.3 64.5 7.0 piperidiue piperidine154-7 73.0 8.7 13.4 73.3 8.3 13.4

The following examples will serve to illustrate a conoriginal wasobtained as a blue image within a matter of venient method ofmanufacturing heat-sensitive copying seconds. sheets which can bethermographically exposed in heat- Example 4 conductive association witha graphic original to produce excellent reproductions within a matter ofa few A ileat'iensltlve copymg Paper pgeparefl exactly.as Seconds.described in Example 3 except that isat1n-3-d morphol1de Example 1(Indole Compound No. 6) was employed 1n place of isatin-3-dipiperidide.An excellent copy of the graphic ISat111-3-d1P1PeY1d1de (Indole 1 0f theabove table) original was obtained as a blue image within a matter wasdissolved in a solution of Vinylite VYLF resin, a f d copolymer of vinylchloride and vinyl acetate (containing Example 5 about 85 to 88% vinylchloride and having a molecular weight of about 6000). The solution wasthen coated A Solution of grams of isatln 'I 1n on a Paper support andthe Solvent evaporated h 100 cc. of ethanol was added to a solution of1.8 grams dry, heat-sensitive copying sheet was placed with the supof A-Y P y s port side in contact with a graphic original and exposures-methylphenol (P1161101 in 100 Of ethanolto inf d radiation was madethrough the h p i- The solution remained clear after the addition of thetive layer, according to the method described-in Miller Phenol componentTO the resulting Solution was et al. US. Patent 2,844,733, issued July22, 1958. The added 100 of a solution of Ethocel y cellugraphic i inal,hi h ont i d line copy, suchas v lose) in methanol. The resultingviscous solution was typewritten characters, developed a heat patterninthose then coated on tfaflslucent P p Stoclf and allowed areascontaining the line copy and caused the produc- 'Y- pp of i dry coatlngWas Placed 111 tion of a blue image in the associated heat-sensitivecopywfltact a lq 011811131 and Passed f ing material. The portions ofthe copying sheet which thermosraphlc' ps devlce of the yp ed were incontact with areas of the original containing no Patent that the fadlammtypewritten characters did not undergo any visible passed first throughthe heat-Sensitive ps/ s sheet and h i then to the graphic original. Anexcellent blue-on-white It may be desirable to stabilize the imagesproduced l 0f the graphic 0118111511 Was Obtallledaccording to the aboveprocess to ambient radiation. It Exam le 6 has been found that theheat-sensitive material can be p overcoated with a transparent layercontaining an ultra- A solution of 1.25 grams of3-piperidino-3-morphoviolet absorbing compound, such as9-benzalfluorene, 5- lino isatin in 100 cc. of methanol was added to 1.8benzal-3-n-cetyl 2 phenylimino 4 thiazolidone, etc., grams of the samephenol used in Example 5, dissolved to achieve greater stability. in 25cc. of ethanol. To the resulting clear solution Example 2 were thenadded 100 cc. of a 5% solution of polyvinyl butyral in methanol. Theresultmg viscous solution was Tetrachlorohydroquinone was dissolved in asolution then coated on translucent paper stock and allowed to ofVinylite VYLF in Z-butanone and the solution coated dry. The dry coatingwas then exposed to a graphic on ordinary paper. After drying, the layerwas then original as described in Example 5, yielding an excellentblue-on-white print. i

overcoated with a polyvinyl butynal layer containing The contrast of theprints was increased considerably by incorporating baryta or titaniumdioxide in the polyvinyl butal coatings or by coating a separatesolution of polyvinyl butal containing the white pigment over theheat-sensitive layer. Ifdesired, the pigmented layer can be coatedbeneath the heat-sensitive layer or on the support side of thesupporting surface.

Example 7 The following solutions were prepared:

A. 100 grams of a solution of polystyrene in ethylene chloride.

B. 2.4 grams of indole compound No. 8 in 60 grams of ethylene chlorideand 20 grams of methanol.

C. 2.0 grams of phenol compound No. 6 dissolved in 20 grams of ethylenechloride.

To the polystyrene solution were added 2.0 cc. of piperidine followed bythe warm solution C. Solution B was warmed on the steam bath andfiltered directly into the stirred polystyrene solution A. The mixtureWas then coated on a suitable translucent paper support and dried.

Exposure of the coating as described in Example 6 gave excellentreproduction of the graphic original as a blue on-white image.

If desired, platsicizers, such as butylphthalate, or antioxidants, suchas bntylated hydroxyanisole can be added to the solutions in order tolower the triggering temperature of the thermo graphic product.

Example 8 The following solutions were prepared:

A. 50 grams of a 10% solution of polystyrene in benzene.

B. 1.2 grams of indole compounds No. 8 in 50 grams of benzene and gramsof methanol.

C. 1.0 gram of phenol compound No. 6 in grams of benzene.

D. 1.0 cc. of piperidine.

The above ingredients were combined as described above in Example 7, andthe resulting, clear viscous solution was coated on a translucent papersupport and the coating dried.

Exposure of the dried coating as described above gave an excellentreproduction of a graphic original as a blueon-white image. If desired,a matting agent, such as finely-divided silica or dispersedpolyethylene, can be added to the above solutions inorder to improve thesurface characteristics of the product. The addition of these materialscan conveniently be made at the time of addition of the piperidine.

Example 9 Component A.--A solution of 100 grams of 2-(2,4-ditert.amylphenoxyacetamino) 4,6-dichloro-5-methylphenol (Phenol No. 6) in 400ccs. of ethyl acetate was filtered while hot and added to a solution of1000 grams of 10% bone gelatin in water. To the solution were added 300ccs. of distilled water and 160 ccs. of 5% alkanolB dispersing agent(sodiumisobutyl-naphthalene sulfonate) at 40 C. After vigorous stirring,the dispersion was run through the colloid mill three times at a settingof 3 to 5 microns. The dispersion was chill-set at 40 F., noodled anddried on wire screens at 75 F. for two days under a vacuum of inches andfor an additional two days at 90 F. under avacuum of inches.

Component B.A solution of 40 grams of 3-piperidino- 3-morpholinoisatinin 1600 ccs. of 1,4-dioxane and 400 ccs. of methanol was filtered andpoured into 8 liters of distilled'water containing 80 ccs. of piperidineat a temperatnre of- 8 to 10 C. After stirring for /2 hour, theprecipitate was filtered by suction and washed three times on a filterwith cold, distilled water, the last water wash containing 1%piperidine. The precipitate was then airdried at room temperatureleaving fine, creamy-white grams of Component A in 1500 ccs. ofdistilled water at 40 C., adding 31 grams of reprecipitated Component B,stirring and running three times through the colloid mill at a settingof 2 to 5 microns. Just prior to coating, 5 ccs. of 5% saponin wereadded. For each 10 square feet of coating, 200 grams of thereconstituted dispersion were weighed out and 0.5 cc. of formalin added.

The reconstituted dispersion was coated on an ordinary onion skin paper,10 inches wide, at the rate of 21 feet per minute. Best results wereobtained with an air knife set a inch. The coating averaged about 9 to10 grams per square foot of emulsion or about 0.8 gram/square foot ofsolids. Exposure of the dried coating as described above gave anexcellent reproduction of a graphic original as a .blue-on-white image.

Our invention can be further illustrated by reference to theaccompanying drawing in which Figure 1 is a cross-sectional view of athermographic copying sheet wherein the heat sensitive components areincorporated in separate layers. In Figure l, a suitable support 10 iscoated with a layer 11 comprising a phenol compound 12. Over layer 11 iscoated layer 13 comprising particles of indole compound 14.

Figure 2 is a cross-sectional view of a thermographic copying materialwherein both heat-sensitive ingredients are incorporated in the samelayer. In Figure 2, the copying material comprises a support 10 coatedwith a heat-sensitive layer 15 having dispersed therein a phenolcompound 12 and an indole compound 14.

In Figure 3, there is illustrated an assembly suitable for producingfacsimile copies using the particular heatsensitive material depicted inFigure 2. In Figure 3, a graphic original 16, having printed material 17thereon, is placed in contact with the uncoated surface of support 10having coated thereon a heat-sensitive layer 18. Upon exposure of theassembly to infrared radiation supplied by any suitable source, such asan infrared lamp in combination with a suitable reflector, a facsimilecopy 19 of the printed character of the original is reproduced as thedarkened portion shown in the drawing.

If desired, the source of infrared radiation can be arranged so that therear surface of the original receives the infrared radiation, althoughin such cases it may be convenient to have an insulating surface appliedto the rear surface of the original in order to minimize loss of theheat generated in the infrared absorbing graphic pattern in theoriginal. Alternatively, the heat-sensitive layer of the copyingmaterial can be placed in contact with the printed characters of theoriginal (i.e., 17 of the drawing), and the assembly then exposed eitherfrom the side of the original or the rear side of the copying sheet.Theseadaptations are well understood by those skilled in the art and areillustrated in domestic and foreign patents. See, for example, MillerU.S. Patent 2,663,657, issued December 22, 1953.

When a colloidal binding agent is employed in combination with theiridole compounds of our invention, alone or in combination with aphenol compound or a compound containing an enolizable keto-methylenegroup, the amount thereof can bevaried in order to control the contrastof the resulting copy. These effects are well understood by thoseskilled in the art. Various esthetic effects can be produced by addinginert pigments or colorants to the colloidal dispersion or to one of theprotected layers applied to the supporting surface or over theheat-sensitlve material, as indicated above.

It has also been found that ninhydrine compounds can be'employed inplace of certain of the indole compounds of our invention to provideexcellent thermographic copies. Such ninhydrine derivatives can beprepared by condensing'one of the heterocyclic secondary 9amines-mentioned above, such as piperidine, etc., together withninhydrin.

The surface temperatures reached on the recording materials used in ourinvention can vary considerably, depending upon the particular indolecompound employed and the presence or absence of an auxiliarycolor-forming component, such as a phenol compound, or a compoundcontaining an enolizable ketomethylene group. The heat-sensitivematerials used in our invention may undergo a color change at atemperature as low as about 45 to 50 C., or a considerably highertemperature, such as 125 C., may be required in order to effect thedesired color change. Of course, where paper or some other supportsubject to distortion or charring is used, the selection of ingredientsshould be made so that the desired color change occurs at a temperaturebelow the distortion or charring temperature of the support (which maycomprise such materials as cellophane, cellulose acetate film, paper,wood, leather, etc.)

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

What we claim and desire to secure by Letters Patent of the UnitedStates is:

1. A heat-sensitive, copying sheet comprising a support and coated onsaid support a heat-sensitive area containing a compound selected fromthe class represented by the following general formula:

morpholine,

wherein R represents a member selected from the class consisting of ahydrogen atom and an alkyl g oup, Q and Q1 each represents thenon-metallic atoms necessary to complete a monocyclic nucleus containingonly one nitrogen atom, said nucleus containing an unsubstituted carbonatom in the 3-position with respect to said nitrogen atom, and Drepresents the atoms necessary to complete a benzene ring, saidheat-sensitive area being disposed on said support so that upon exposureof said heat-sensitive area to radiant energy in heat-conductiveassociation with a pattern containing portions highly absorptive of saidradiant energy and portions substantially nonabsorptive of said radiantenergy, said heat-sensitive area undergoes a rapid color change only inthose areas in heat conductive association with those areas highlyabsorptive of said radiant energy, said heatsensitive, copying sheetbeing stable at room temperature, being substantially insensitive tovisible radiations and being non-sticking at 125 C.

2. A heat-sensitive, copying sheet comprising a support and coated onsaid support a heat-sensitive area containing (a) a compound selectedfrom those represented by the following general formula:

wherein R represents a member selected from the class consisting of ahydrogen atom and an alkyl group, Q and Q each represents thenon-metallic atoms necessary to complete a monocyclic nucleus containingonly one nitrogen atom, said nucleus containing an unsubstituted carbonatom in the 3+position with respect to said nitrogen atom, and Drepresents the atoms necessary to complete a benzene ring and (b) acompound selected from the class consisting of phenols and compoundscontaining an enolizable keto group, said compounds (a) and (b) beingmaintained in physically-distinct relationship, so that upon exposure ofsaid heat-sensitive area to radiant energy in heat-conductiveassociation with a pattern containing portions highly absorptive of saidradiant energy and portions substantially nonabsorptive of said radiantenergy, said heat-sensitive area undergoes a rapid color change only inthose areas in heat conductive association with those areas highlyabsorptive of said radiant energy, said heat-sensitive, copying sheetbeing stable at room temperature, being substantially insensitive tovisible radiations and being nonsticking at C.

3. A heat-sensitive copying sheet comprising a support and coated onsaid support a heat-sensitive area containing (a) a compound selectedfrom those represented by the following general formula:

( H a-C ll 01 --NH C-Rs wherein R represents a member selected from theclass consisting of an alkyl group and an aryl group, R represents amember selected from the class consisting of hydrogen atom and an alkylgroup, and X represents a member selected from the class consisting of ahydrogen atom, a halogen atom, and a non-basic organic substituent, (2)a S-pyrazolone compound containing a hydrogen atom in the 4-position and.(3) a compound containing an acyclic group, said compounds (a) and (b)being maintained in physically-distinct relationship, so that uponexposure of said heat-sensitive area toinfrared energy in heatconductiveassociation with a pattern containing portions highly absorptive of saidinfrared energy and portions substantially nonabsorptive of saidinfrared energy, Said heat-sensitive area undergoes a rapid color changeonly in those regions in heat-conductive association with those regionshighly absorptive of said infrared'cnergy, said 11 heat-conductive,copying sheet being stable at room temperature, being substantiallyinsensitive to visible radiation and being non-sticking at 125 C.

4. A heat-sensitive, copying sheet comprising (1) a fibrous support and(2) a heat-sensitive colloid layer having dispersed therein particles of(a) a compound selected from those represented by the'following' generalformula:

wherein R represents a member selected from the class consisting of ahydrogen atom and an alkyl group, Q and Q each represents thenon-metallic atoms necessary to complete a monocyclic nucleus containingonly one nitrogen atom, said nucleus containing an unsubstituted carbonatom in the 3-position with respect to said nitrogen atom, andDrepresents the atoms necessary to complete a benzene ring, andparticles of (b) a compound selected from the class consisting ofphenols and compounds containing an enolizable keto group, saidparticles (11) and (b) being maintained in a physically-distinctrelationship, so that upon exposure of said heat-sensitive, copyingsheet to radiant energy in heat-conductive association with a patterncontaining portions highly absorptive of said radiant energy andportions substantially nonabsorptive of said radiant energy, saidheat-sensitive copying sheet undergoes a rapid color change only inthose areas in heat-conductive association with those areas highlyabsorptive of said radiant energy, saidlheatsensitive copying sheetbeing stable at room temperature, being substantially insensitive tovisible radiation and being substantially non-sticking at 125C.

5. A heat-sensitive, copying sheet comprising (1). a thin paper supporthaving low thermoconductivity, (2) a colloid layer having dispersedtherein discrete particles of a compound selected from those representedby the following general formula:

wherein R represents a member selected from the: class consisting of ahydrogen atom and an alkyl group, Q andQ each represents, thenon-metallic atoms necessary to complete a monocyclic nucleus containingonly one nitrogen atom, said nucleus containingan unsubstituted. carbonatom in the 3-position with respect to said nitrogen atom, and Drepresents the atoms necessary to complete a benzene ring, andcontiguous to said colloid layer (2), a colloid layer having dispersedtherein discrete particles of a compound selected from the classconsisting of phenols and compounds" containing an enolizable ketogroup, so that upon-exposureof said heatsensitive copying sheet toradiant energy inlheat=conductive association with a pat-tern containingportions highly absorptive of said radiant energy and portionssubstantially nons-absorptive of said'radiant energy, saidheat-sensitive copying sheet undergoes a rapid color change only-inthose areas in heat-conductive association with those areashighlyabsorptive of said radiant energy, said hea-t-sensi tive, copying;sheet; being stable;at.room temperature;

being substantially insensitive to visible radiation and beingnon-sticking at C.

6. A- heat-sensitive, copying sheet comprising (1) a thin paper supporthaving low thermoconductivity and (2) a heat-sensitive colloid areahaving dispersed therein (a) discrete particles of a compound selectedfrom those'represented by the following generalformula:

wherein R represents a member selected from the class consisting ofahydrogen atom and an alkyl group, Q and Q each represents thenon-metallic atoms necessary to complete a monocyclic nucleus containingonly one nitrogen atom, said' nucleus containing an unsubstituted carbonatom in the 3-position with respect to said nitrogen atom, and Drepresents the atoms necessary to complete a benzene ring, and (b)discrete particles of a compound selected from the class consisting of(A) those compounds represented by the following general formula:

ll Cl NEG-13:

wherein R represents a member selected from the class consisting of analkyl group and an aryl group, R represents a member selected from theclass consisting of a hydrogen atom and an alkyl group, and X representsa member selected from the class consisting of a hydrogen atom, ahalogen atom, and anon-basic organic substituent, (B) a 5.-pyrazolonecompound containing a hydrogen atom in the'4-position, and (C) acompound containing an acyclic group, said particles (a) and (b) beingmaintained in physically-distinct relationship, so that upon exposure ofsaid heat-sensitive copying sheet to infra-red energy in heat-conductiveassociation with a pattern containing portions highly absorptive ofvsaid infrared energy and portions substantially non-absorptive of saidinfrared energy, said heat-sensitive copying sheet undergoes a rapidcolor change only, in those areas in heat-conductive, association withthose regions highly absorptive of saidinfrared energy, saidheat-conductive, copying sheet being stable at'room temperature, beingsubstantially insensitive tovisible radiation and being non-sticking at125 C.

7. A heat-sensitive, copying sheet, as defined in claim 4; whereinsaidparticls (a), comprise isatin-3-dipiperidide and said particles (b)comprise tetrachlorohydroquinone.

8. A heat-sensitive, copying sheet, as defined in claim 4, wherein saidparticles (:2) comprise isatin-B-dipiperidide and said particles (b).comprise dichlorol1ydroquinone.

9. A heat-sensitive, copying sheet, as defined in claim 4, wherein saidparticles- (a) comprise isatin-B-dimorpholide and said particles (1))comprise 2-(2,4-di-tert.- amylphenoxyacetamino-4,6-dichloro-5-methylphenol.

10. A heat-sensitive, copying sheet, as defined in claim 13 14 4,wherein said particles (a) comprise 3-piperidino-3- heat-sensitive atthe temperatures employed in producing morpholinoisatin and saidparticles (b) comprise 2-(2,4- visible copies from said heat-sensitivecopying sheet. (ltterti'amylPhenoxyacetammo)4,6 dichlom's'methyl'References Cited in the file of this patent p eno 11. A heat-sensitive,copying sheet, as defined in claim 8 UNITED STATES PATENTS 4, whereinsaid heat-sensitive copying sheet is provided 2,740,895 Miller Apr. 3,1956 with a protective outer layer which is substantially non- 2,899,334Grevling Aug. 11, 1959

1. A HEAT-SENSITIVE, COPYING SHEET COMPRISING A SUPPORT AND COATED ONSAID SUPPORT A HEAT-SENSITIVE AREA CONTAINING A COMPOUND SELECTED FROMTHE CLASS REPRESENTED BY THE FOLLOWING GENERAL FORMULA: